(x+1)²+y²=1令x=-1+cosa则y²=1-cos²a=sin²a所以不妨令y=sinax+y=sina+cosa-1=√2(√2/2*sina+√2/2cosa)-1=√2(sinacosπ/4+cosasinπ/4)-1=√2sin(a+π/4)-1所以最小值=-√2-1
=(3-2)×√3=√3
